The present invention relates to accessories for trailers and in particular to an improved tongue jack.
When a trailer is parked and detached from a tow vehicle, a support is required for the trailer tongue. Although other objects might be used, generally a special purpose jack (called a trailer jack or tongue jack) attached to the tongue is used. Trailer jacks generally are mounted vertically, or are pivotable to a vertical position, and have a telescoping portion and a crank for upwardly and downwardly moving the telescoping portion. Such jack provides static support, leveling, and facilitates detaching the tongue from the trailer hitch on the tow vehicle by allowing the tongue to the raised relative to the hitch and thereby disengaging from the hitch. Large trailers generally have significant tongue weight for safety and control. The tongue jack much be able to support the tongue weight, and allow operation without undue effort.
Devices for supporting trailer tongues are well known. U.S. Pat. No. 2,159,395 for “Trailer Control,” describes a pivotable wheel assembly which may be cranked to a down position whereby the trailer tongue is supported. U.S. Pat. No. 2,638,315 for “Trailer Attached Jack,” describes a simple telescoping jack for supporting a trailer tongue. U.S. Pat. No. 2,638,315 for “Trailer Attached Jack,” describes a telescoping tongue jack similar to modern jacks. The jack of the '315 patent includes a crank for turning a screw shaft, which screw shaft is held in place by a thrust bearing, and cooperates with a nut attached to an inner telescoping tube to extend or retract the inner tube.
U.S. Pat. No. 3,314,693 for “Retractable Trailer Tongue Jack,” describes a jack having a screw shaft with a ring gear. A crank turns a pinion gear engaging the ring gear to turn the screw shaft, thereby extending or retracting an inner tube. U.S. Pat. No. 5,435,523 for “Trailer Tongue Jack,” describes a tongue jack with a pair of cooperating beveled gears coupling a crank to a screw shaft.
When known tongue jacks are used with heavy trailers having substantial tongue weight, the thrust bearings require lubrication to reduce wear and provide easy use. Commonly, such lubrication is provided by opening the trailer jack assembly and applying grease to internal parts. Unfortunately, such opening and applying may be a messy operation, and the grease frequently escapes the jack assembly, resulting in the grease on hands and clothing.